Method for producing a smoking product of cellulosic material

ABSTRACT

The preparation of a smoking product of oxidized cellulosic material treated with a dilute solution of an organic acid to fix heavy metal ions by formation of a thermally stable salt followed by the removal of excess acid and reintroduction of an amount of fixing acid up to 1 percent by weight of the cellulosic material for subsequent fixing of heavy metal ions remaining in the cellulosic material or subsequently released therein.

United States Patent lnventors Theodore S. Briskin;

Geoffrey R. Ward, Beverly Hills, Calif. Appl. No. 745,369 Filed July 17, 1968 Continuation-impart of Ser. No. 595,622, Nov. 21, 1966, Patent No. 3,447,539 and Ser. No. 674,994, Oct. 12, 1967. Patented Jan. 19,1971 Assignee Sutton Research Corporation Los Angeles, Calif. a corporation of Delaware METHOD FOR PRODUCING A SMOKING PRODUCT OF CELLULOSIC MATERIAL 14 Claims, No Drawings US. Cl 131/2, 1 17/143 Int. Cl A24b 15/00, D06m 01/14 Field ofSearch 131/2,15,

[56] References Cited UNITED STATES PATENTS 2,131,160 9/1938 Avedikian. 3,364,200 1/1968 Ashton et al 260/212 FOREIGN PATENTS 702,918 2/1965 Canada 131/2 OTHER REFERENCES Sax (Text) DANGEROUS PROPERTIES OF INDUSTRI- AL MATERIALS (1968) Third Edition Reinhold Pub. NYC p. 987 cited.

Primary ExaminerMelvin D. Rein Att0rney-McD0ugall, Hersh, Scott & Ladd ABSTRACT: The preparation of a smoking product of oxidized cellulosic material treated with a dilute solution of an organic acid to fix heavy metal ions by formation of a thermally stable salt followed by the removal of excess acid and reintroduction of an amount of fixing acid up to 1 percent by weight of the cellulosic material for subsequent fixing of heavy metal ions remaining in the cellulosic material or subsequently released therein.

a 1 METHOD FOR PRODUCING A SMOKING PRODUCT OF CELLULOSIC MATERIAL This is a continuation-in-part of our copending applications Ser. No. 595,622, filed Nov. 21, 1966, and entitled Smoking Products, now US. Pat. No. 3,447,539, and Ser. No. 674,994, filed Oct. 12,1967, and entitled Smoking Products and Process for Making Such Products.

As used herein, the term smoking products is meant to refer to and to include tiller material embodied in cigarettes, cigars and for use with pipes and the like,'and mixtures thereof with various proportions of tobacco and including cigarette papers and wrappers used in the preparation of such cigars and cigarettes, and it includes cigarettes, cigars and the like products manufactured with such filler materials and wrappers.

in the aforementioned copending applications, description is made of the preparation of a smoking product suitable for use in cigarettes, cigars or with pipes wherein the smoking product is prepared of relatively pure cellulosic materials subjected to selective oxidation with liquid nitrogen dioxideto convert preferably more than 90 percent of the methylol groups in the cellulosic molecule to yield a product which can be referred to as an oxycellulose or polyuronic acid. The oxidation reactionproduct is further processed by removal'of liquid nitrogen dioxide by vaporization and preferably by washing the oxidized cellulosic product with water and/or alcohol and/or acetone or other solvent for removal of solubilized foreign material, including oils, waxes, latices and the like, which contribute undesirably to the taste and aroma when used as a smoking product in accordance with the practice of this invention.

As further described in the aforementioned copending applications, the oxidized and cleansed cellulosic derivative is further processed by a reduction reaction with borohydrides of an alkali or alkaline earth metal such as sodium or lithium borohydride for reduction of such nitrogen compounds, quinones, ketones, aldehydes and unsaturates as otherwise have a tendency to impart undesirable aroma and taste as the smoking product is burned. The product before or after reduction can be subjected to additional oxidation with a dilute peroxide solution as a means for eliminating further groupings which impart undesirable aroma or taste to the product.

The resulting smoking product is then formulated with rnineralizing agents such as oxalates, glycolates, diglycolates,

lactates, or pivalatcs of such metals as calcium, magnesium, lithium, potassium, barium or strontium, preferably introduced to form the salt internally in the cellulosic derivative for purposes of providing desired ashing characteristics. Instead of fonning the described salts internally in the cellulosic derivative, limited beneficial characteristics can be achieved by external application of such mineralizing agents. As described, the desired internal introduction is achieved by first wetting the cellulosic derivative with metal cation indilute solution for absorption into the cellulosic derivative followed by exposure to the acid anion in solution to precipitate the metal salt in situ in the cellulosic material.

The treatedcellulosic derivatives can be further processed to improve the burning, glow and smoking characteristics by formulation to includes potassium salt, such as potassium ox alatc or by the addition of rubidium or cesium in the form of compounds thereof in amounts within the range of 0.l percent to percent by weight but preferably less than i percent by weight, as described in the copcnding application Ser. No. 623,528, filed Mar. I6, 1967, now abandoned, and entitled Smoking Products and Process for Their Manufactured Smoke generators for improving the appearance of the smoke generated by the product can be introduced as by the in troduction of various fatty acids, esters, others and the like and the aroma and pH characteristics can be achieved by the addition of volatiiizable alknlyzing material such as ammoni um oxalate and the like.

The resulting product is suitable for use as a smoking product alone or in admixture with tobacco to produces smoking product having good taste, good aroma and good appearance.

As the cellulosic raw material, use can be made of various forms of cellulose, such as wood pulp, alpha-cellulose, flax, fibrous carbohydrates, seaweed carbohydrates, bamboo filaments, cotton filaments, hemp, straw, refined paper, rice paper, filamentous gums and even plants and plant leaves and the like fibrous or sheet materials from which noncarbohydrate components have been separated, all of which is hereinafter referred to as cellulosic material.

it is preferred to make use of a purified cellulosic material from which various of the sugars, proteins, chlorophills, flavones, colors, lignins, oils, waxes, resins and latices have been removed since these contribute undesirable odors and tastes to the smoking product.

Purified cellulose is unsatisfactory for use as a smoking product from the standpoint of taste, aroma and burning characteristics. This is believed to stem from the acids and aldehydes that are evolved upon pyrolysis of the cellulose. it has been found that many of the defects of pure cellulose can be greatly alleviated by conversion of the methylol groups to carboxyl groups to produce a product which readily pyrolyzes with complete burning of the cellulose molecule into water vapor, and oxidation products of carbon such as carbon dioxide and low molecular weight compounds which readily volatilize. Thus the object is to achieve selective oxidation of the cellulosic material to convert methylol groups, primarily the methylol groups containing the C carbon, to carboxyl groups, preferably with better than 90 percent conversion. There is no objection to further oxidation beyond 100 percent by conversion of secondary hydroxyl groups as on C and C to monoand diketo groups, so long as cleavage does not occur.

Liquid nitrogen dioxide yields an oxidation reaction that has the desired selectivity and complete wetting of the cellulosic materials can be achieved almost instantaneously with liquid nitrogen dioxide with the result that the oxidation reaction takes place substantially uniformly throughout the cross section of the cellulosic material and at a much more rapid rate whereby a more uniformly and more, completely oxidized product is obtained in less time. Furthermore, liquid nitrogen dioxide, when used in the proportions most suitable for the practice of this invention, quenches and operates immediately to dissipate heat generated by the exothennic reaction so as to avoid the formation of hot spots or nonuniformity in the reactions.

in our copending application Ser. No. 745,221 filed concurrently herewith and entitled A Smoking Product and Method of Preparation," description is made of the oxidation of a cellulosic material by suspension in liquid nitrogen dioxide in the ratio of 1 part by weight cellulosic material to 5 to .1000 parts by weight liquid nitrogen dioxide and preferably 1 part by weight cellulosic material to 25 to 50 parts by weight of liquid nitrogen dioxide. The reaction therein is carried out at a temperature within the range of 15 to 65 C and at an autogenous pressure when the reaction temperature exceeds 21 C (boilrange of 20 to 45 C, depending somewhat upon the amount 1 of moisture present in the reaction medium, whereby the reac-' tion medium is rendered relatively nonelectrically conductive so that the presence of water in the reaction medium will not result in attack or degradation of the cellulosic material to be oxidized and wherein the formulation to include aqueous medium in the reaction of liquid nitrogen dioxide operates also to adjust the specific gravity of the reaction medium in the direction towards the specific gravity of the cellulosic material whereby suspension of the cellulosic material in the reaction medium is easier to achieve and maintain. The result is a more rapid and uniform oxidation reaction of the cellulosic material to produce a better product at a more rapid rate.

In our copending application Ser. No. 745,134, now US. Pat. No. 3,478,752 filed concurrently herewith and entitled Cellulosic Smoking Product and Method in the Preparation of Same, description is made of selective oxidation of cellulosic material with liquid nitrogen dioxide in which an oxygen containing gas is introduced into the reaction medium during oxidation of the cellulose to accelerate the rate of oxidation and to reconvert nitric oxide, formed in the oxidizing medium, to nitrogen dioxide thereby to achieve more uniform oxidation at a higher rate.

In our further copending application Ser. No. 745,404 filed concurrently herewith and entitled A Smoking Product of Cellulosic Material Subjected to a Nitrogen Dioxide Oxidation and a Mild Oxidation with Peroxide," description is made of the oxidation of cellulosic raw material with nitrogen dioxide followed by a further gentle oxidation with a peroxide to effect a possible destruction of nitro groups.

This invention is addressed to overcoming the undesirable taste and aroma that is observed upon burning a smoking product containing heavy metal ions, especially in the presence of the oxidized cellulosic material. Even trace amounts of calcium, magnesium, aluminum, iron, cobalt and copper ions, especially in the presence of the oxidized cellulosic material, give a sharp acidic odor when the smoking product is used in a cigarette, cigaror pipe.

These metallic ions form corresponding metal salts with polyuronic acids, such as are formed upon oxidation of the cellulosic material. These polyuronic acid salts of the residual heavy metal ions are thermally unstable and break down during burning of the smoking product to give various odorous aldehydes, ketones, acids and the like.

Thus it is an object of this invention to fix the ions of the heavy metals present in the smoking product in a manner to inactivate the heavy metal ions as factors contributing to any bad taste, odor or aroma of the smoked product.

The important concept of this invention resides in a method and means for fixing the ions of heavy metals by reaction with a suitable acid to form a thermally stable salt; in which the reaction to form the salt with the acid takes preference over salt formation with polyuronic acids; in which the salt that is formed is more thermally stable than the corresponding salt of polyuronic acid so that the metal ions will remain tied up while the oxidized cellulosic material burns out of the smoking product; and in which a small amount of fixing acid is intentionally introduced into the smoking product as insurance for typing up residual metallic ions which might remain or which might subsequently be released.

While the concepts of this invention have application primarily to oxidized cellulosic material, as described in the aforementioned copending applications and the applications filed concurrently herewith, it will be understood that this concept of fixing objectionable heavy metal ions with acceptable acids to form thermally stable salts that resist deterioration during burning will have beneficial use in any cellulosic material used or adapted to be processed into a smoking product.

As the fixing acid, it is preferred to make use of oxalic acid, but use can be made of other acids such as pivalic acid, tannic acid, lactic acid, glycolic acid, diglycolic acid and the like. The acids are employed in aqueous solution containing from 0.1 percent to percent by weight of the acid and preferably in an amount within the range of 0.1 percent to 1 percent by weight. When the treating solution contains more than 10 percent by weight acid, the oxidized cellulose tends to be taken into the solution. This undesirable feature can be obviated by incorporating an amount of alcohol, such as methyl, ethyl, propyl alcohol, in the aqueous medium in amountsup to 25 percent. in fact, use of an alcoholic solution is desirable when use is made of a treating solution containing more than 4 percent by weight acid.

The acid'solution is introduced into the cellulosic material in an amount to provide sufficient acid to satisfy the heavy metal ions present in the cellulosic material or the oxidized cellulosic material. The amount introduced is determined by odor tests with the pyrolyzing cellulosic material according to the impurities present in each batch. Application can be made by spraying onto the cellulosic material or the cellulosic material, especially when in the form of a paper web, can be passed through the solution for pickup by absorption of the desired amount of acid.

Treatment with the acid solution to fix the metallicions is preferably made at a temperature within the range of 0 to 30 C. There is no need to heat beyond 30 since the oxalic or other fixing acids are readily soluble in the aqueous medium in the desired proportions. Salt formation .by the metallic ions and acid takes place quite rapidly under the conditions described without the need for heat or long reaction time.

It is important to avoid excesses of free fixing acid in the treated product since such excesses tend to impart an acrid taste to the smoking product.

A further concept of thisinvention is to return to the treated cellulosic material a measured amount of a oxalic, tannicand the like acids to make acid available for reaction in forming thermally stable salts with metal ions that have escaped reaction during the described fixing treatment or which might subsequently be released during processing or aging or pyrolysis of the cellulosic material. Small amounts of oxalic acid or other fixing acid up to 0.2 percent by weight of the cellulosic material can be introduced into the smoking product without harmful effect and this amount is more than sufficient to fix additional metallic ions that might appear in the smoking product.

For these purposes, the measured quantity of oxalic or other acid is dissolved to form a dilute solution in aqueous medium with which the cellulosic material is impregnated and dried for uniform distribution. For economical reasons, it is preferred to effect application by spraying ontothe treated cellulosic material with a solution containing the acid in as high a concentration as possible so as to minimize the cost of application and drying. it is difficult to achieve uniform distribution with spray application. In order to avoid undesirable effects from the standpoint of odor from such nonuniform distribution, it is preferred to make use of oxalic acid generators, such as potassium hydrogen oxalate, ammonium oxalate or esters of methyl, ethyl, or propyl alcohol with tartaric acid which yield oxalic acid on decomposition.

The following examples are given by way of illustration, but not by way of limitation, of the practice of the described concepts of this invention.

EXAMPLE 1 Thin paper formed of purified cellulose pulp is selectively oxidized, as described in the aforementioned copending applications, by introduction into a reaction vessel with fifty times its weight of liquid nitrogen dioxide and maintained with agitation for 6 to 8 days at 20C The liquid oxidizing medium is drained for separation from the oxidized cellulose and the latter is vacuum evaporated until free of nitrogen oxides.

The oxidized cellulosic material is processed in accordance with the practice of this invention by immersion in ten times its weight of an aqueous solution containing 0.5 percent by weight oxalic acid at a temperature of about 25 C. After about one hour of treatment, the solution is drained from the oxidized cellulosic material and the oxidized cellulosic material is copiously washed with water andthe material is allowed to dry.

EXAMPLE 2 Purified wood pulp is treated to fix heavy metal ions contained therein by introduction into a vessel with five times its volume of an aqueous solution containing 1 percent by weight oxalic acid. The material is maintained in a state of agitation in the vessel for from 2 to 3 hours and the acidic solution is drained for separation from the cellulosic material. The latter is washed in at least two separate washings with deionized water to remove excess oxalic acid and then 0.2 percent by weight oxalic acid based upon the dry weight of cellulosic material dissolved in aqueous medium to form a percent solution which is then sprayed upon the treated cellulosic material with constant stirring for uniform distribution.

EXAMPLE 3 Thin strips of paper formed of purified cellulosic pulp are selectively oxidized by introduction into a reaction vessel with twenty-five times its weight of liquid nitrogen dioxide containing 1.5 percent by weight water. The oxidation reaction is carried out under autogenous pressure, and with constant stirring at a temperature of 35 o 40 C. Reaction is continued for 24 to 36 hours after which the liquid oxidizing medium is drained for separation, from the oxidized cellulosic material. The latter is then washed with two times its volume of anhydrous liquid nitrogen dioxide and then vacuum evaporated until free of nitrogen oxides.

The oxidized cellulosic material is then treated in ac cordance with the practice of this invention by introduction into a vessel with five times its weight of an aqueous solution containing 0.25 percent by weight of oxalic acid and treatment is continued for several hours with constant agitation at about ambient temperature.

The acidic medium is drained for separation from the oxidized cellulosic material and the latter is then copiously washed with, water to effect removal of excess oxalic acid. After drying, 0.5 percent by weight of potassium hydrogen oxalate, based on thedriedcellulosic material, dissolved in aqueous medium, is sprayed onto the cellulosic material to in troduce free fixing acid for fixing residual heavy metals remaining in, the oxidized cellulosic material or subsequently released therein.

EXAMPLE 4 The purified cellulosic pulp istreated with oxalic acid solution as in Example 2 and then the treated cellulosic material is oxidized and subsequently treated again with oxalic acid solution as in Example 3.

EXAMPLE 5 Examples 1 to 4 are repeated with the substitution of tannic or lactic acid for oxalic acid.

EXAMPLE 6 Example} is repeated but with substitution of ammonium oxalate oresters of tartaric acid and methyl, ethyl or propyl alcohol for, the potassi rm hydrogen oxalate in equivalent amounts.

EXAMPLE 1 Oxidized cellulose is introduced into'areaction vessel having a mixer with sufiicient water therein to provide a convenient mobility of the slurry when stirred. Acetic acid is added to a level of about 2 percent by weightacetic acid. Lime isadded in anamountto provide an ash level of about 5 percent when completely absorbed by ,the oxidized cellulose. The pH of the solution thus rises from 4 to about 5. As the calcium istaken up by the oxidizcd cellulose, the pH of the system will fall back toabout 4. After 5 minutesatarnbient temperature, oxalic acid is added in a stoichiometric amount and the pH of the system immediately drops to about 3. After 5 to 10 minutes at ambient temperature and as the oxalic acid is absorbed into the fiber by the calcium to form calcium oxalate inside the fiber, the pH of the system will rise to b about 4 again.

The cycle is repeated five more times to produce an oxidized cellulose containing enough internally dispersed calcium oxalate to give about 20 percent to 24 percent ash when burnt.

After the final cycle, the treated oxidized cellulosic material is thoroughly washed with water containing about 25 percent by weight ethyl alcohol, to remove surplus oxalic acid and the cleansed oxidized cellulosic material is dried to about 40 percent atmospheric relative humidity.

After drying, one part by weight of aqueous solution of oxalic acid dissolved in an amount corresponding to 0.25 percent by weight of the oxidized cellulosic material is reintroduced with mixing into two parts by weight of product which is again dried to about 40 percent to 50 percent atmospheric relative humidity. 1

The cellulosic material, processed in accordance with Examples l to 7, finds use as a smoking product having odor and taste properties much improved over the corresponding materials without treatment with the acidic medium or introduction of extra fixing acid to the cellulosic material. It is preferred, however, further to process the cellulosic material produced in accordance with the practice of this invention to effect further modification for use as a smoking product as by subjecting the oxidized cellulosic material to a reduction reaction with borohydride or hydrogen, as previously described, and/or by subjecting the oxidized cellulosic material to a mild oxidation with peroxide, as previously described, and by introduction of various agents for combination with the cellulosic material including the addition of mineralizing or ashing agents such as calcium oxalate; the introduction of agents for controlling burning rate and glow, such as potassium, cesium or rubidium salts; agents for controlling smoke generation; neutralizing agents such as ammonium or amine salts, and agents for imparting desired color and aroma to the smoking product.

It will be understood that changes may be made in the details of formulation and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. in the preparation of a smoking product of oxidized cellulosic material, the steps of treating the cellulosic material with an aqueous solution containing an acid selected from a group consisting of oxalic, pivalic, lactic, glycolic and diglycolic acids, which forms a thermally stable salt in the form of the oxalate, glycolate, diglycolate, lactate or pivalate with heavy metal ions present in the cellulosic material to fix the heavy metal ions in the smoking product, washing the excess acid from the treated cellulosic material, and reintroducing free fixing acid selected from a group consisting of oxalic, pivalic, lactic, glycolic and diglycolic acids, or compounds releasing such acid into the cellulosic material in an amount within the range of 0.1 to 10 percent by weight for subsequent reaction with heavy metal ions that remain in the cellulosic material and are subsequently released therein.

2. The process as claimed in claim 1 in which the heavy metal ions present in the oxidized cellulosic material and reacted with the fixing acid to form thermally stable salts are of at least one of the metals copper, iron, cobalt, calcium, magnesium, aluminum and potassium.

3. The process as claimed in claim 1 in which the acid is present in the aqueous solution in an amount within the range of 0.1 percent to 10 percent by weight.

4. The process as claimed in claim 1 in which the acid is present in the aqueous solution in an amount within the range of 0.1 percent to 1 percent by weight.

5. The process as claimed in claim I in which the treatment with the acidic solution is carried out at a temperature within the range of 0 to 30 C.

6. The process as claimed in claim l-in which the fixing acid and the acid introduced into the treated cellulosic material is oxalic acid.

7. The process as claimed in claim I in which the acidic component is reintroduced into the treated oxidized cellulosic material in an amount less than 1 percent by weight.

8. The process as claimed in claim 1 which includes the'step of subjecting the cellulosic material to selective oxidation with nitrogen dioxide after treatment with the acidic medium to fix heavy metal ions.

9. The process as claimed in claim 1 which includes the step of subjecting the oxidized cellulosic material to selective oxidation with nitrogen dioxide prior to treatment with the acidic medium to fix the heavy metal ions.

10. The process as claimed in claim 1 which includes the steps of subjecting the oxidized cellulosic material to selective oxidation with nitrogen dioxide after treatment with the acidic medium to fix heavy metal ions and then repeating the treatment with acidic medium to fix heavy metal ions subsequent to oxidation of the cellulosic material.

11. The process as claimed in claim 1 in which the acidic component is introduced into the treated oxidized cellulosic material in an amount up to 0.5 percent by weight ofthe cellulosic material.

12. The process as claimed in claim 1 in which the acidic component introduced into the oxidized cellulosic material after treatment is in the form ofa compound selected from the group consisting of potassium hydrogen oxalate, ammonium oxalate and a lower alcohol ester of tartaric acid.

13. The process as claimed in claim 9 in which, when the acid is present in the treating solution in an amount greater than 4 percent by weight, the treating solution is in the form of an aqueous alcoholic solution.

14. The process as claimed in claim 13 in which the alcohol is present in an amount up to 25 percent by weight. 

2. The process as claimed in claim 1 in which the heavy metal ions present in the oxidized cellulosic material and reacted with the fixing acid to form thermally stable salts are of at least one of the metals copper, iron, cobalt, calcium, magnesium, aluminum and potassium.
 3. The process as claimed in claim 1 in which the acid is present in the aqueous solution in an amount within the range of 0.1 percent to 10 percent by weight.
 4. The process as claimed in claim 1 in which the acid is present in the aqueous solution in an amount within the range of 0.1 percent to 1 percent by weight.
 5. The process as claimed in claim 1 in which the treatment with the acidic solution is carried out at a temperature within the range of 0* to 30* C.
 6. The process as claimed in claim 1 in which the fixing acid and the acid introduced into the treated cellulosic material is oxalic acid.
 7. The process as claimed in claim 1 in which the acidic component is reintroduced into the treated oxidized cellulosic material in an amount less than 1 percent by weight.
 8. The process as claimed in claim 1 which includes the step of subjecting the cellulosic material to selective oxidation with nitrogen dioxide after treatment with the acidic medium to fix heavy metal ions.
 9. The process as claimed in claim 1 which includes the step of subjecting the oxidized cellulosic material to selective oxidation with nitrogen dioxide prior to treatment with the acidic medium to fix the heavy metal ions.
 10. The process as claimed in claim 1 which includes the steps of subjecting the oxidized cellulosic material to selective oxidation with nitrogen dioxide after treatment with the acidic medium to fix heavy metal ions and then repeating the treatment with acidic medium to fix heavy metal ions subsequent to oxidation of the cellulosic material.
 11. The process as claimed in claim 1 in which the acidic component is introduced into the treated oxidized cellulosic material in an amount up to 0.5 percent by weight of the cellulosic material.
 12. The process as claimed in claim 1 in which the acidic component introduced into the oxidized cellulosic material after treatment is in the form of a compound selected from the group consisting of potassium hydrogen oxalate, ammonium oxalate and a lower alcohol ester of tartaric acid.
 13. The process as claimed in claim 9 in which, when the acid is present in the treating solution in an amount greater than 4 percent by weight, the treating solution is in the form of an aqueous alcoholic solution.
 14. The process as claimed in claim 13 in which the alcohol is present in an amount up to 25 percent by weight. 